Flexible wave guide



' March 12, 1957 J. M. LAMB FLEXIBLE WAVE GUIDE Filed April 2, 195a INVENTOR- AGENT Q a u United States Patent FLEXIBLE WAVE GUIDE John M. Lamb, Newton, N. 1., assignor to Co-Operative Industries, Inc., Chester, N. J., a corporation of New Jersey Application April 2, 1953, Serial No. 346,375

2 Claims. (Cl. 333-95) This invention relates to improvements in flexible wave guides. In particular, the invention is directed to an improved construction of corrugated, rectangular wave guides used for the propagation of high frequency electronic waves.

Broadly, there are three classes of flexible wave guides as: the helical interlock guide, the segmental guide, and the corrugated guide. In the first mentioned, flexing is the result of relative movement of the loosely engaging helices of which the guide is formed. In the segmental guide there is likewise a condition of relative movement in flexure between the individual segments used in the guide construction. Corrugated guides, either of transverse or helical corrugations, provide improvements electrically over the first two types, but are limited in their resistance to flexing since they depend for flexibility upon bending of the walls of the corrugations. Where corrugated guides must withstand repeated flexing or vibration, there may be a concentration of stresses tending to promote failure of the relatively thin sections of material from which the guides are formed.

It is the principal object of my invention to provide a flexible corrugated wave guide which will withstand long term, severe flexing and vibration. It is a further object of the invention to provide a guide of this class with improved resistance to concentration of flexing. A still further object of the invention is to add to the useful life of flexible, corrugated wave guides without materially adding weight or size thereto.

With these and other important objects in mind, I provide a guide innercore having transverse corrugations similar to those of the innercore described in my co-pending application, Serial No. 257,581 filed November 21, 1951, of null-seam construction, being formed from a corrugated strip folded to rectangular, transverse configuration and having a seam centrally lengthwise of a broad face. End fittings are secured to the core and a stress limiting mechanical covering is placed directly over the guide core and is fixed thereto in a prescribed manner at certain locations. The stress limiting covering is flexible and may be further embedded in a rubber or plastic covering of the kind regularly used in wave guide practice for added mechanical protection.

In the drawings, wherein I have illustrated a preferred physical embodiment of my invention,

Figure 1 is a plan view of a wave guide according to my invention, partly broken away to illustrate details of construction,

Figure 2 is a view similar to Figure 1 showing discontinuous use of the stress limiting covering, and

Figure 3 is an enlarged fragmentary view in central, longitudinal cross section to show the guide of my invention at the attachment of a typical flange fitting.

Referring to Figure 1, my improved wave guide consists, in part, of a straight length of flexible wave guide innercore 10, the core being of rectangular, hollow cross section in accordance with theory and practice relating to the propagation of electromagnetic waves. The

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material preferred for applications of this nature is brass l and the internal surfaces are preferably electroplatedwith silver in order to reduce attenuation. The corruga-* tions are regular and I prefer, as hereinabove stated, to use null-seam guide construction according to my 00-- pending application, although the principles of stress regulation which I use may also be applied to waveguides of other known types. To each end of the core- 10 is soldered or brazed, or otherwise aflixed, a suitable wave guide flange fitting 11, thus permitting the guide assembly to be secured to components of the particular electrical system with which it is used. The length of.

the guide will be determined by its association with other units of the electrical system and an inherent advantage in the use of flexible wave guides is the property of curving to suit irregular lines of installation.

Referring to Figure 3 for a consideration of the termination of the guide as at the left hand end of Figure l, fitting 11 is provided with a rectangular aperture 12 through which core 10 may be fitted to extend flush with the external face of the fitting. Aperture 12 is sufiiciently long to accommodate several core corrugations and is a snug fit with the outside of the corrugations and thus, alignment may be carried to the flange for accurately matching the flexible guide with a corresponding rigid wave guide or with an accessory component. Extending to the right from aperture 12 within flange 11 is an enlarged rectangular opening 13 serving, in part, as a well for solder or brazing material 14 securing the flange 11 and core 10 as a unit.

It will be noted at this juncture, see also Figure 1, that innercore 10 is covered with an open mesh, relatively tight basket weave braid 15 consisting of multiple strands of fine bronze wires which extend into the fitting 11 to the extent of the solder Well 13 and which are embedded in solder at that position. Thus, the braid ends together with the flange and core become unitary within the flange, but braid does not extend into the snug fit aperture 12 to accentuate problems of electrical mis-match which are present at wave guide joints. Solder 14 fills the core undulation to the face of the flange, but does not entirely fill the enlarged aperture 13, leaving a partial opening short of the inner face of flange 11 to permit the usual rubber or synthetic covering 16 to be locked therein during molding and to extend into the vent holes 17 adjacent the end of the flange and to thus be further locked in place.

Like construction is employed at the right hand flange joint. The assembled guide is thus constructed so that flexing is restricted to that permitted by the braided covering, which is well within the elastic limit of the innercore corrugations, the braid being anchored at both ends and being tightly developed over the core. It is, of course, possible to regulate the degree of braid tension and to vary the size and shape, number and lay of the braid Wires to attain the desired flexing characteristics for the wave guide.

In the modification of Figure 2, there is illustrated a guide assembly constructed according to the principles outlined above, but with discontinuous application of the basket weave braiding 15, the braid extending from within the fittings 11 and being terminated at specific intermediate locations 18 and being bonded to the core at those locations as by the use of solder 14'. In this manner, guides may be permitted a greater degree of flexing over unbraided portions where stresses are not severe and where flexibility is desirable yet restricted at locations where stresses would otherwise produce fatigue in the innercore material.

Having thus described my invention, I claim:

1. In a flexible wave guide assembly adapted for the.

propagation of high frequency electrical current, in com- 2,785,382 Patented Mar. 12, 1957 bination, a flexible, corrugated, hollow, rectangular innercore, terminalfittings bonded over the ends of the core, said fittings being provided with rectangular sizing apertures closely matching and axially aligned with the external surface of the core at the open endtherec-f and with counter-apertures continuing from the sizing apertures to the opposite end of the fittings, and a basket weave metal wire braid over the core bonded to said core and terminated within said counter-apertures.

2. In a flexible wave guide for the propagation of high frequency electrical current, in combination, a corrugated, hollow, rectangular core section, hollow wave guide connector fittings secured over the core in axial alignment therewith and terminating flush with the ends thereof, said fittings being provided with rectangular sizing apertures for the core and with counter-apertures adjacent the sizing apertures, a metallic braid covering the core, said braid further extending to within the fittings and being secured therein, but terminating short of the flush ends of the innercore and fittings, and a plastic, molded chafing resistant covering over the core between the fittings, said plastic covering also extending partly within said counterapertures of said fittings and being locked therein.

References Cited in the file of this patent UNITED STATES PATENTS 996,899 Witzenmann July 4, 1911 2,696,834 Carr Dec. 14, 1954 FOREIGN PATENTS 5,085 Great Britain Apr. 5, 1887 

